The Challenge of Rearend Leaf Springs

Like any cars of the ’70s muscle car era, they weren’t easy to get hooked up then, and they’ve only worsened over the years. The problem typically was that the rearend leaf springs easily wrapped up under hard acceleration, causing severe wheelhop that shook the car. The more you had under the hood and the more tire on the pavement, the worse the rear spring wrapup, and the more the car would wheelhop. If it got bad enough, the car would break rearend pieces.

Previous Solutions and Limitations

A lot of modifications were tried, including stiffer springs and ladder bars, and shock options that had varying degrees of success, but the only things that really took care of axle hop were Super Stock rear springs, shackles and a heavy-duty pinion snubber made for S/S and early Pro Stock cars. Another, later approach was to back-half the car, which also allowed for larger rear tires. In the end, what everyone faced was the combination of leaf springs that, by their very design, are prone to axle control issues, and a unibody construction that limits strong enough attachment points for more serious remedies.

Advancements in Suspension Technology

At the time, few gave much thought to swapping out the leaf springs for anything else—there were no such things as coilover shocks or the newer ShockWaves. As coilover shocks became more readily available, four-bar setups became more commonplace, particularly in racing, but most of those were custom made and installed. Both coilover springs and ShockWaves are compact and allow for effective spring rate changes. As racing hardware began being adapted to the street, muscle cars were the happy benefactors of some of this technology.

Air Ride Technologies’ Innovative Approach

The folks at Air Ride Technologies understood this and began looking at the whole picture as they devised new air spring suspensions. Owner Bret Voelkel has continued to not only develop his expanding line of four-bar applications, but also to make a point of demonstrating how well his air sprung suspension works in off-road situations, as well as on road courses and at the dragstrip, in addition to normal road conditions.

The Birth of the AirBar Rear Suspension

The whole muscle car series of AirBar rear suspensions stemmed from a need to make Voelkel’s own Mustang handle with big power and fat guy tires. Seeing the similarities between many of the cars of the same era, this technology was applied one by one to a succession of other muscle cars. That’s how the E-body got a healthy new rear suspension.

Installation Process

The way they work is by completely eliminating the original leaf spring arrangement, substituting a reinforced cradle that attaches a triangulated four-bar setup. A more labor-intensive way to install a four-bar would be to back-half the car, but that requires a lot of cutting, fabrication, body stiffening and a suspension that fits. Most people with these older muscle cars really think twice before cutting them apart to that extent. What the folks at Air Ride Technologies did was to use as much of the original mounting locations as possible to bolt in the reinforcing structure. They did a great job of this, requiring only a few drilled holes.

Benefits of the Four-Bar Setup

The four-bar arrangement contributes a tremendous amount of rigidity and precision movement of the rearend components, and this keeps the axle from twisting the pinion and hammering the floor pan—there is no four-bar wrap. Because this is a triangulated four-bar, the side-to-side movement potential is significantly reduced, as you’d have to both compress one bar and stretch the opposite bar to force the axle to move side to side, or to cause the axle housing to rotate backward. If you look at drag cars with a similar setup, then you know there have been a number of solutions to wrap and axle sway, but you will also note that most of those are simply not streetable.

Ride Quality and Performance

More recent technology has shown that ultra-stiff suspensions not only lack any degree of acceptable ride quality and hamper cornering in unfortunate ways, but they are also not as effective for over-the-road control compared to a more “live” suspension. The AirBar kit, which is installed here, has been carefully designed using the proven qualities of ShockWave air spring/shocks to provide E-body Mopars with a triple threat—great ride, exceptional handling and much improved hookup. Here’s how it’s done.